1. Field of the Invention (Technical Field)
The present invention relates generally to the field of direct write deposition.
2. Background Art
Note that the following discussion refers to a number of publications and references. Discussion of such publications herein is given for more complete background of the scientific principles and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Various techniques may be used for deposition of electronic materials, however thick film and thin film processing are the two dominant methods used to pattern microelectronic circuits. Recently, ink jetting of conductive polymers has also been used for microelectronic patterning applications. Thick film and thin film processes for deposition of electronic structures are well-developed, but have limitations due to high processing temperatures or the need for expensive masks and vacuum chambers. Ink jetted conductive polymers have resistivities that are approximately six orders of magnitude higher than bulk metals. Thus, the high resistivity of ink jetted conductive polymers places limitations on microelectronic applications.
U.S. Pat. No. 4,485,387 discloses direct write of electronic circuits onto ceramic targets using an apparatus that feeds a high-viscosity ink through the orifice of a writing pen. One jetting technique, disclosed in U.S. Pat. Nos. 5,772,106 and 6,015,083, dispenses low-melting temperature solder using a process similar to the process used in piezoelectric ink jetting. The minimum feature size attainable with this method was reported to be approximately 70-100 microns. Deposition of metals onto low-temperature targets is not disclosed. U.S. Pat. Nos. 4,019,188, 4,825,229, 5,032,850 and 5,814,152 describe methods for direct deposition of thin films from droplets, particles, or vapors entrained in a carrier gas. U.S. Pat. Nos. 4,825,229 and 5,032,850 disclose a printing method wherein a sublimable dye is mixed with a carrier gas and jetted through an orifice for the purpose of printing color characters or images. The process disclosed in U.S. Pat. No. 5,814,152 requires laser melting and ablation of aerosolized material, and is not capable of localized deposition. U.S. Pat. No. 4,019,188, by Hochberg et al. discloses an aerosol jet apparatus for ink printing applications. The apparatus uses ultrasonic atomization and a pressurized chamber ending in an orifice, to form a jet of aerosolized ink entrained in a carrier gas. Hochberg discloses the use of relatively large exit orifices—the reported orifice diameters range from 200 to 825 microns—and a minimum deposited feature size of 50 microns. The invention of Hochberg does not use a sheath gas to form an annular flow for the purpose of focusing the aerosol stream and preventing accumulation of material at the exit orifice, is limited to the deposition of ink onto paper, and does not disclose a process for aerosolization and deposition of viscous inks or inks composed of particle suspensions.
The Maskless Mesoscale Material Deposition (M3D™) apparatus, on the other hand, provides a method for the direct write of fine features of electronic and biological materials onto low-temperature or high-temperature targets. The M3D™ deposition flowhead uses a series of nested channels that produce an annular aerodynamic focusing of an aerosol-laden carrier gas stream. The as-deposited line features may be as small as approximately 5 microns, and may be treated thermally or using laser radiation. The M3D™ process deposits liquid molecular precursors or precursors with particle inclusions, and uses a subsequent processing step that converts the deposit to the desired state. The precursor viscosity may range from approximately 1 to 1000 centiPoises (cP), as opposed to ink jetted solutions, which are typically confined to around 10 cP. The M3D™ process may also deposit aerosolized materials onto many targets with damage thresholds as low as 100° C., and is a maskless process that can be performed under ambient or inert environmental conditions.
The use of detachable nozzles for material deposition in microelectronic and fluid dispensing applications has been reported. One of the most common microelectronic applications of detachable nozzles is that of wire bonding. U.S. Pat. No. 4,886,200 discloses a capillary tip for bonding a metal wire to a target. The metal wire is passed through the capillary, and ultrasonic vibrations are applied to the metal to bond the wire to the surface of the target. U.S. Pat. No. 6,325,269 discloses a wire bonding capillary that decreases the extraction resistance of the wire during the bonding process using a funnel-shaped bore and a tapered section at the capillary exit. U.S. Pat. No. 6,309,891 discloses an invention for printing small volumes of liquid samples using spring-loaded plungers and a wire bonding capillary in fluid contact with reservoirs containing the liquid to be deposited.